For many years, the usual method of treating a diseased intraocular lens has been to remove the diseased lens and replace it with an IOL implant. Two surgical procedures have each been found useful in the removal of a diseased lens, i.e., extracapsular cataract extraction and phacoemulsification. Extracapsular cataract extraction involves the removal of a diseased lens in a relatively intact condition through the use of forceps or an instrument similar thereto. Phacoemulsification involves contacting a diseased lens of an eye with a vibrating cutting tip of an ultrasonically driven surgical handpiece to emulsify the lens. Once emulsified, the lens is aspirated from the eye. Both surgical procedures require the cornea (or sclera) and the anterior lens capsule of the eye to be opened to allow access to the interior of the lens capsule. Once within the lens capsule, the diseased lens is removed and an intraocular lens (IOL) implant is positioned therein.
Visual acuity deficiencies such as myopia (nearsightedness) and hyperopia (farsightedness) are typically corrected with the use of refractive lenses such as spectacles or contact lenses. Although these types of lenses are effective in correcting a wearer's eyesight, many wearers consider the lenses inconvenient. The lenses must be located, worn at certain times, removed periodically and may be lost or misplaced. The lenses may also be dangerous or cumbersome if the wearer participates in athletic activities or suffers an impact in an area near the eyes.
The use of surgically implanted IOLs as a permanent form of refractive correction has been gaining in popularity. As noted above, IOL implants have been used for years in aphakic eyes as replacements for diseased natural crystalline lenses, which have been surgically removed from the eyes. Many different IOL designs have been developed over past years and proven successful for use in aphakic eyes. The successful IOL designs to date primarily include an optic portion with supports therefor, called haptics, connected to and surrounding at least a part of the optic portion. The haptic portions of an IOL are designed to support the optic portion of the IOL in either the anterior or posterior of an eye.
Commercially successful IOLs have been made from a variety of biocompatible materials, ranging from more rigid materials such as polymethylmethacrylate (PMMA) to softer, more flexible materials capable of being folded or compressed such as silicones, certain acrylics, and hydrogels. Haptic portions of the IOLs have been formed separately from the optic portion and later connected thereto through processes such as heat, physical staking and/or chemical bonding. Haptics have also been formed as an integral part of the optic portion in what is commonly referred to as "single-piece" IOLs.
Softer, more flexible IOLs have gained in popularity in recent years due to their ability to be compressed, folded, rolled or otherwise deformed. Such softer IOLs may be deformed prior to insertion thereof through an incision in the cornea of an eye. Following insertion of the IOL in an eye, the IOL returns to its original pre-deformed shape due to the memory characteristics of the soft material. Softer, more flexible IOLs as just described may be implanted into an eye through an incision that is much smaller, i.e., 2.8 to 3.2 mm, than that necessary for more rigid IOLs, i.e., 4.8 to 6.0 mm. More rigid IOLs must be inserted through an incision in the cornea slightly larger than the diameter of the IOL's optic portion. Larger incisions have been found to be associated with an increased incidence of postoperative complications such as induced astigmatism.
After IOL implantation in either phakic or aphakic eyes, some patients experience visual distortions commonly referred to as "halos". Halo visual distortions are caused by light entering a patient's eye reflecting off of the edge of the IOL. For this reason, some IOLs are produced with glare reduction zones. Glare reduction zones are typically located around an outer peripheral edge of the optic portion of the IOL and may be colored, opaque or patterned to block or diffuse light.
Unfortunately, depending on the style and material of the IOL, manufacturing an IOL with a glare reduction zone using today's techniques is often times difficult and in some cases impossible for a variety of reasons.
Because of the noted shortcomings in today's techniques for imparting a glare reduction zone on IOL implants, there is a need for a process capable of imparting a glare reduction zone on most if not all IOL styles to minimize halo visual distortions and the like.